The invention relates to a tensioner for a seat belt.
Belt tensioners serve for quickly retracting or reducing a possibly present belt slack so that the seat belt can fully develop its protective effect for the occupant. In the case of so called linear tensioners which make use of a linear displacement of a piston in a cylinder tube for tensioning the seat belt a return stop serves for preventing the piston from returning to its initial position after the tensioning operation. In view of the installation space in vehicles which is available to a restricted extent only the overall length of the tensioners is a substantial criterion for installation.